The central aim of the proposed research is to investigate nucleotide sequences which are involved in the regulation of genes. Transcription signals (promoters and operators) of selected systems will be investigated. (1) Transcription Control Sequences in Bacteriophage lambda for the Immediate Early, Rightward Promoter-Operator of cro mRNA and the cI Promoter Associated with the Lysogenic State. A deoxypolynucleotide with sequence complementary to part of cro mRNA will be synthesized. This deoxypolynucleotide will be hybridized to the separated strand of lambda DNA, elongated by appropriate enzymes (polymerases) into the control region for cro mRNA and cI mRNA, and the elongated primer sequenced. These two genes are controlled by DNA found in the same region of bacteriophage lambda and therefore can be sequenced with the same primer. The DNA contribution to gene regulation will also be examined by sequencing mutant strains from this region where the level of either cro mRNA or cI mRNA has been altered. Sequence comparison with the wild type will provide important information on what DNA parameters are essential for regulation. (2) Transcription initiation and Spacer Sequences for S5 RNA from Xenopus laevis, rat, mouse, rabbit and HeLa cells. All these eukaryotic systems have S5 RNA with identical sequence near the 5'-end. Therefore, a deoxypolynucleotide with sequence complementary to this region will be synthesized. The spacer and transcription initiation site from Xenopus laevis will first be examined. The sequence will be obtained by primer dependent repair synthesis using the deoxypolynucleotide and the appropriate S5 DNA strand. The investigation will then be extended to S5 DNA regulatory sites in other eukaryotic systems.